Process for measuring endotoxin and apparatus used therefor

Abstract

Endotoxin contents in samples can be determined qualitatively or quantitatively, singly or in parallel, with high precision in a short time by a process comprising applying a light to each sample solution, measuring an initial transmitted light amount I0 and a transmitted light amount at a time t, I(t), to give a ratio R(t) = I(t)/I0, and judging a gelation point by a threshold value of R(t), or further obtaining a gelation time from the gelation point. An apparataus used therefor is also disclosed.

What is claimed is: 
     
       1. A process for measuring an endotoxin which comprises mixing a sample with an endotoxin gelating reagent to give one or more sample solutions,   applying a light to each sample solution,   measuring a transmitted light amount at an initial stage I 0  and that after a reaction time t, I(t), in each sample solution to give a ratio R(t)=I(t)/I 0 , and   judging a gelation point by the ratio R(t) reaching a certain value in the range of 75 to 97%.   
     
     
       2. A process according to claim 1, wherein the initial value I 0  is a maximum initial value I 0 .max, an average initial value I 0 .av, a minimum initial value I 0 .min, or an initial value at a special point of time "ts" I 0 .ts. 
     
     
       3. A process according to claim 1, which further comprises obtaining a gelation time T G  from a time required for reaching the gelation point from the mixing of the sample and the endotoxin gelating reagent, and   determining the endotoxin content in the sample.   
     
     
       4. A process according to claim 3, wherein two or more sample solutions are used in parallel. 
     
     
       5. A process according to claim 3, wherein the initial value I 0  is a maximum initial value I 0 .max, an average initial value I 0 .av, a minimum initial value I 0 .min, or an initial value at a special point of time "ts", I 0 .ts. 
     
     
       6. An apparatus for measuring an endotoxin comprising one or more optical systems each comprising a light source, a sample solution-holding vessel, and a means for detecting transmitted light amounts,   a constant temperature bath for maintaining the optical systems at a constant temperature and keeping the vessel still,   a means for correcting the sensitivity of the optical systems and for judging a gelation point by the ratio R(t)=I(t)/I 0 , wherein I 0  is a transmitted light amount at an initial stage and I(t) is a transmitted light amount after a reaction time t, reaching a certain value in the range of 75 to 97%,   a means for instructing the initiation of measurement of transmitted light amounts connected to the means for correction and judgment, and   a timer for measuring the time passed from the initiation of measurement of transmitted light amounts for each optical system in parallel and independently and connected to the means for correction and judgement.   
     
     
       7. An apparatus according to claim 6, wherein the sample solution-holding vessel is a cuvette having an inner diameter of 6 to 12 mm. 
     
     
       8. An apparatus according to claim 6, wherein the means for instructing the initiation of measurement is a switch which can give the instruction to two or more sample solution-holding vessels independently. 
     
     
       9. An apparatus according to claim 6, wherein the means for correcting the sensitivity of the optical systems and for judging a gelation point comprises one or more devices having functions of (a) starting the timer by the initiation of measurement instructed by the means for instructing the initiation of measurement,   (b) beginning to measure transmitted light amounts,   (c) measuring transmitted light amounts with the lapse of time,   (d) conducting the correction of the sensitivity of each optical system,   (e) judging a gelation point, and   (f) stopping the timer at the time of judging the gelation.   
     
     
       10. An apparatus according to claim 6, wherein the means for correcting the sensitivity of the optical systems and for judging a gelation point has a means for transferring data of transmitted light amounts or data of measured time to one or more outer computers. 
     
     
       11. An apparatus according to claim 6, which further comprises at least one device connected to the means for correcting the sensitivity of the optical systems and for judging a gelation point and selected from the group consisting of a measuring state display, a gelation judgement display, a gelation time display and a measuring time display. 
     
     
       12. An apparatus according to claim 11, which further comprises a printer connected to the means for correcting the sensitivity of the optical systems and for judging a gelation point. 
     
     
       13. A process for measuring an endotoxin which comprises mixing a sample with an endotoxin gelating reagent to give two or more sample solutions,   applying a light to each sample solution,   measuring a transmitted light amount at an initial stage I 0  and that after a reaction time t, I(t), in each sample solution to give a ratio R(t)=I(t)/I 0 , and   judging a gelation point by the ratio R(t) reaching a certain value,   obtaining a gelation time T G  from a time required for reaching the gelation point from the mixing of the sample and the endotoxin gelating reagent, and   determining the endotoxin contents in the samples in parallel.   
     
     
       14. A process according to claim 13, wherein the certain value of R(t) for judging the gelation point is in the range of 75 to 97%. 
     
     
       15. A process according to claim 13, wherein the sample is a liquid sample in an amount of 0.1 ml and the endotoxin gelating reagent is a Limulus amoebocyte lysate reagent in an amount of 0.1 ml. 
     
     
       16. A process according to claim 13, wherein the sample is a liquid sample in an amount of 0.2 ml and the endotoxin gelating reagent is a freeze-dried Limulus amoebocyte lysate reagent. 
     
     
       17. A process according to claim 13, wherein the transmitted light amount at an initial stage I 0  is a maximum initial value I 0 .max. 
     
     
       18. A process according to claim 13, wherein the transmitted light amount at an initial stage I 0  is an average initial value I 0 .av. 
     
     
       19. A process according to claim 13, wherein the transmitted light amount at an initial stage I 0  is a minimum initial value I 0 .min. 
     
     
       20. A process according to claim 13, wherein the transmitted light amount at an initial stage I 0  is an initial value at a special point of time "ts", I 0 .ts. 
     
     
       21. An apparatus for measuring an endotoxin comprising a plurality of optical systems each comprising a light source, a sample solution-holding vessel, and a means for detecting transmitted light amounts, and conducting the measurement of a plurality of samples in parallel,   a constant temperature bath for maintaining the optical systems at a constant temperature and keeping the vessel still,   a means for correcting the sensitivity of the optical systems and for judging a gelation point,   a means for instructing the initiation of measurement of transmitted light amounts connected to the means for correction and judgement, and   a timer for measuring the time passed from the initiation of measurement of transmitted light amounts for each optical system in parallel and independently and connected to the means for correction and judgment.